Liquid crystal display device is widely used as an image display device for TV set, personal computer and so forth, for its low power consumption and possibility of thinning. The liquid crystal display device is configured by providing polarizing plates on both sides of a liquid crystal cell, wherein the polarizing plate is configured by a polarizing film, in which iodine or dye is adsorbed and aligned, sandwiched from both sides with translucent resin layers. The translucent resin layers, directed to protect a polarizer, are preferably configured using cellulose acylate film.
Other than being used indoors like the TV sets and so forth, there have been increasing opportunities for the liquid crystal display device to be used outdoors, typically as incorporated into mobile devices. There has therefore been a demand for development of the liquid crystal display device more durable under high temperatures and high humidity than before. The cellulose acylate film is, however, liable to change in size due to absorption or desorption of water under variable temperature and humidity, and is therefore likely to be stressed. It has been becoming clear that the cellulose acylate film, when stressed, develops a large photoelastic coefficient, which results in leakage of light when a liquid crystal display screen is observed under a specific condition.
Accordingly, Patent Literature 1 for example proposes a cellulose ester film which contains a cellulose ester, and a polymer compound configured by polymerizing N-vinyl-2-pyrrolidone as a monomer. On the other hand, Patent Literature 2 proposes a cellulose ester film which contains a cellulose ester, and as a plasticizer a hydroxyl group-containing hydrogenated petroleum resin.
The cellulose ester film proposed in Patent Literature 1 is advantageous in terms of small leakage of light, and the cellulose ester film proposed in Patent Literature 2 is advantageous in terms of high translucency, low breeding-out, and high stability. Both of them have, however, been not fully satisfactory in terms of keeping good performance of polarizer, since the polarizer degraded with time when used for a long time under high temperatures and high humidity. Patent Literature 2 was also found to suffer from a problem of insufficient improvement in the leakage of light.